Quite a number of electronic components are mounted on a printed-wiring board. Heretofore, in a process for mounting such electronic components on a printed-wiring board, an electronic-component automatic mounter has been used.
Most of the currently prevalent electronic-component automatic mounters have been developed with high-speed manufacturing in mind. Therefore, an electronic-component feeding device for use with the automatic mounter has also been developed with a view to automatically feed a large volume of electronic components, as a key function.
Among electronic components, a chip-type electronic component, such as a chip resistor or a chip capacitor which is a passive component, has the largest number of items or kinds thereof and a large quantity of them are used. The chip-type electronic component includes a wide variety of components, such as an inductor and a diode, and it is estimated that the production number of chip-type electronic components in the world including Japan reaches one trillion per year.
Currently, in a process for mounting the large volume and wide variety of chip-type electronic components on a printed-wiring board, most of the chip-type electronic components are packed onto a tape having a width of 8 mm (8-mm tape), and fed to an electronic-component automatic mounter through a tape feeder. The tape packed with the electronic components (hereinafter referred to as “component tape”) is wound onto a reel, and one reel with a diameter of 180 mm contains about 5,000 to 10,000 of the components.
An electronic component other than the chip-type electronic components, for example, a large-size component, such as an IC and other semiconductor components, incapable of being packed onto the 8-mm tape, is packed onto a wider tape having a width, for example, of 12, 16, 24, 32 or 44 mm, and fed to an electronic-component automatic mounter through a tape feeder. In addition to the component tape-based feeding, some large-size electronic components, particularly ICs, are also packed onto a matrix tray and fed in the form of the tray packed with the electronic components (hereinafter referred to as “component tray”).
The currently prevalent electronic-component automatic mounters can be roughly classified into the following two types: (1) a first type designed to pick up an electronic component at a fixed component feeding section, transfer the component to a given position where a printed-wiring board is fixedly positioned, and mount the electronic component on the printed-wiring board; and (2) a second type designed to rotate a turret at a fixed position so as to receive a given electronic component at a movable component feeding section, and mount the component on a printed-wiring board which is placed on an X-Y table and moved to a given position. That is, the second type is designed to perform simultaneous parallel operations of sucking (pickup) and mounting.
Both of the first and second types of electronic-component automatic mounters are combined with either one of the component tape-based feeding and the component tray-based feeding. Thus, in a process for mounting all of required electronic components using a single electronic-component automatic mounter, the mounter has to be combined with a number of tape feeders and/or a tray feeding device capable of feeding a number of component trays containing plural kinds of electronic components. This causes a problem in that there is an excessive increase in the area of a component feeding section, and a resulting excessive increase in the size and cost of the electronic component automatic mounter. Thus, it is often the case that the number of number of kinds of electronic components is minimized, and a plurality of electronic component automatic mounters are used in combination to complete a mounting operation for a single printed-wiring board.
As mentioned above, a mainstream technique for feeding electronic components to an electronic component automatic mounter is the component tape-based feeding, and other components incapable of using the component tape-based feeding are typically fed by the component tray-based feeding. Most of the component tapes and trays are fed to the mounter directly in the form of a packaging used for shipment/transport from a component supplier. For example, when chip-type electronic components are supplied in the form of the tape-and-reel packaging, about 5,000 components are contained in one reel. This reel is put on a tape feeder to feed the component tape to the mounter at high speed. Some electronic components are frequently used, that is, a few dozens are mounted per printed-wiring board, and some electronic components are less frequently used, that is, only one is mounted per printed-wiring board. If electronic components of which only one is to be mounted per printed-wiring board are fed by a reel containing 5,000 components, all the components in one reel will be consumed only after completion of a mounting operation for 5,000 printed-wiring boards. In contrast, a reel containing frequently-used components will be frequently replaced.
Similarly, electronic components to be fed by the component tray-based feeding are packed onto different trays depending on component suppliers and kinds of electronic components. In this case, electronic components are packed in each of the trays on a kind-by-kind basis. Thus, a tray feeding device for feeding such many kinds of electronic components is required to have a capacity of loading a number of component trays containing many kinds of electronic components. Specifically, the tray feeding device is designed to allow several dozens of different component trays to be loaded there into in a stacked manner and allow a required one of the electronic components in the trays to be picked up in a random manner.
The currently prevalent electronic-component automatic mounters are designed to automatically feed all kinds of components at high speed using the mainstream tape feeder and tray feeder, regardless of whether or not they are frequently used.
Thus, in the existing circumstances, when the currently prevalent electronic-component automatic mounter and electronic-component feeding device are used for mounting many kinds of electronic components on a small lot such as one to several lot manufacturing type of printed-wiring boards, the manufacturing is completed in a moment, after considerable time is spent on rearranging the electronic component feeding device, creation of a mounting program for the plurality of mounters, etc.
Currently, when many kinds of electronic components are mounted on a small lot such as one to several lot manufacturing type of printed-wiring boards, there are the following two cases: one where the components are manually mounted one-by-one while manually soldering them; the other where an existing high-volume manufacturing line is temporarily shifted to a low-volume manufacturing line. In the latter case, the printed-wiring board is apt to be manufactured in a number greater than a required number, and the extra printed-wiring boards will be stored for an upcoming manufacturing, because of an extremely short manufacturing time as compared to a fairly long setup time.
Further, in some cases, for the purpose of reducing a time needed for rearrangement of the electronic-component feeding device in the event of a setup operation, electronic components required for plural types of printed-circuit boards are pre-loaded onto the feeding device so as to allow required components to be fed simply by calling a corresponding software program, in the event of the setup operation. In this case, an extremely large number of electronic-component feeding devices have to be installed in an electronic-component automatic mounter. This often raises the need for providing a plural number of the mounters. The resulting manufacturing capacity is too high for mounting electronic components on the small-lot manufacturing type of printed-wiring board, and an extravagant amount of equipment investment is required.
Further, despite a current trend that the mounting for a large-volume manufacturing type of printed-wiring boards has been increasingly shifted to low-wage countries, and the fabrication of prototype boards and the mounting for a high-mix low-volume manufacturing type of printed-wiring boards has increased in developed countries, the establishment of a suitable manufacturing system for the current situation, or the development of an electronic-component feeding device and an automatic mounting apparatus for a high-mix low-volume manufacturing is still quite preliminary.
A mounting system suitable for a high-mix low-volume manufacturing is required to allow a setup operation to be completed in a short period of time. A mounting system comprising the currently prevalent electronic-component automatic mounter and electronic-component feeding device requires that a good deal of time be spent for a setup operation, such as rearrangement of the feeding device, and adjustment of balance in manufacturing volume between a plurality of the mounters and creation of a mounting optimization program. Further, in order to reduce a time needed for rearrangement of the feeding devices during a setup operation, electronic components required for plural types of printed-wiring boards are pre-loaded onto the feeding device to allow required components to be fed simply by calling a corresponding software program in the event of the setup operation, as described above, or each manufacturing line is fixedly used for a specific type of printed-wiring boards. In either case, an extravagant amount of equipment investment is required, and it cannot be said that the electronic components can be manufactured efficiently.
Among electronic components, most of the chip-type electronic components, such as a chip resistor and a chip capacitor which are passive components having the largest number of kinds thereof and a large quantity of which are used, are currently fed by an 8-mm tape feeder (electronic-component feeding device). In a process for feeding many kinds of electronic components, it is required to use a number of 8-mm tape feeders. If a number of currently-prevalent 8-mm tape feeders are installed in an electronic-component automatic mounter, a component feeding section will occupy a large area in the mounter. In an electronic-component automatic mounter having a fixed component feeding section, a distance which a mounting head is required to move to pick up the component is significantly increased. In an electronic-component automatic mounter having a movable component feeding section, a length of the component feeding section and a total installation space of the mounter are undesirably increased. The increase in size or length of electronic-component automatic mounter causes an increase in cost thereof Moreover, the 8-mm tape feeder itself is costly, and thereby a total cost of the mounting system including the mounter and the large number of 8-mm tape feeders will be hugely increased. The 8-mm tape feeder also involves a problem that less-frequently-used chip-type electronic components are inevitably contained therein in an excessively large number.
Further, despite the advance in downsizing of electronic devices and printed-wiring boards, the size of the electronic-component automatic mounting apparatus cannot be reduced due to slow-up in downsizing of the electronic-component feeding device.
The component tape-based feeding involves various problems, such as difficulties in reducing a component cost due to the need for a taping process and a costly tap material; poor ability to feed less-frequently-used components due to the large number (about 5,000 to 10,000) of chip-type electronic components contained in one reel supplied in the form of a tape-and-reel packaging; adverse affects on environmental conservation due to the tape being scrapped after use while the reel is recyclable; high transport and storage costs due to the large size of the package for the reel; and occurrence of a defective solder joint in a high-density mounting due to paper fragments of a paper tape.
If less-frequently-used large-size components are fed to an electronic-component automatic mounter directly in the form of a packaging at a time of shipment from a component supplier, a component tape will cause a problem due to an excessively large number of electronic components contained therein, and a component tray will cause problems due to an excessive increase in the area occupied or space for installing a tray feeding device when a plurality of component trays are arranged parallel to each other on a plane surface, or complexity in structure and increase in cost when a plurality of different component trays are arranged in a stacked manner. In a process for feeding a high-mix low-volume manufacturing type of electronic components, many kinds of electronic components may be mixedly contained in a common tray and the component tray fed to a common component feeding section. However, this is impracticable, because a large number of different electronic components having various sizes can be contained in a common tray only if the tray has a number of pockets formed in conformity to the respective sizes of the electronic components.
While the electronic components may be manually arranged on a common tray, it is practically difficult to arrange without error the electronic components at their correct positions.
In the process for mixedly feeding many kinds of electronic components in the common component feeding section, it is necessary to provide a sequencer for picking up electronic components from a packaging shipped from a component supplier and rearranging the electronic components on the component feeding section in the order of mounting. However, the currently prevalent electronic-component feeding device has no electronic-component sequencer unit for this purpose.
In the process for mixedly feeding many kinds of electronic components arranged on the component plate in the order of mounting, if a failure of mounting one of the electronic components on a printed-wiring board occurs, the failed-to-be-mounted electronic component has to be re-fed to the mounter to complete the mounting for the printed-wiring board. Thus, it is necessary to establish a process for reliably re-feeding a non-sequenced electronic component corresponding to the sequenced and failed-to-be-mounted component, with a high degree of accuracy.
In a process for manually mounting electronic components on a printed-wiring board one-by-one, the electronic components are manually soldered while attaching them onto the printed-wiring board, in most cases. Despite of difficulties in obtaining stable quality, this process has been often used as a quick-fix solution for fabricating one to several printed-wiring circuit boards. However, an electronic component is apt to have a smaller size and a higher mounting density. For example, currently prevalent chip-type electronic components have a minimum size of 0.6 mm×0.3 mm. It is extremely difficult to anchor such a micro-size component with tweezers, and manually solder the component.
Moreover, in the high-density mounting process, a distance between adjacent electronic components is in the range of 0.1 to 0.2 mm, and thereby a manual mounting operation is attended with much difficulty. The number of high-density printed-wiring boards unsuitable for a manual mounting operation is increasing, and a manual mounting of electronic components is thus becoming more and more difficult.
In addition, while a complete operational manual and training for operators are essential to allow operators to mount without error many kinds of electronic components at their correct positions, the preparation of such a complete operational manual and the operator's training for fabricating one to several printed-wiring boards have not been done in the existing circumstances, and thereby it is difficult to ensure adequate quality.
Some electronic components having a junction formed in a back surface of a component package in a grid pattern, such as a CSP (Chip Scale Package) or a micro PGA (Pin Grid Array), cannot be manually soldered, and a multi-pin component, such as an IC, involves significant difficulty in being manually mounted with adequate accuracy. The number of electronic components unsuitable for a manual mounting operation is increasing.
Thus, in view of quality, it is optimal to perform a mounting operation using a fully automatic mounting apparatus. While the mounting apparatus may have a low mounting speed in a mounting process for a high-mix low-volume manufacturing-type of printed-wiring boards, it should be able to feed a low volume of many kinds of electronic components, and mount the components with a high degree of accuracy at a low cost.
While the manufacturing system using a plurality of mounters in combination can facilitate improving productivity, it involves a problem in that a long preparation time is needed for alternation of mounting programs for the plurality of mounters, rearrangement of a plurality of electronic-component feeding devices, and adjustment of a balance in manufacturing volume between the plurality of mounters, in the event of a setup operation. Thus, the current electronic component mounting line is suitable for a high-volume manufacturing, but not for a high-mix low-volume manufacturing.
If less frequently-used electronic components are fed to a plurality of mounters through tape feeders, an excessive number of stock electronic components is undesirably fed to a component feeding section in each of the mounters.
In a manufacturing system provided with a plurality of mounters associated with each other and with various related apparatuses, such as a solder cream printing machine and a reflow furnace, each of the mounters and related apparatuses cannot be operated with optimal efficiency due to an unbalance in manufacturing volume and manufacturing capacity between the mounters and related apparatuses. Moreover, there is a need for simultaneously setting up the associated mounters and related apparatuses in the event of a setup operation. Thus, this system is unsuitable for a high-mix manufacturing.